%0 Journal Article %A G. A. Serëgin %T On the differentiability of local extremals of variational problems of the mechanics of rigidly viscoplastic media %J Izvestiâ vysših učebnyh zavedenij. Matematika %D 1987 %P 23-30 %N 10 %I mathdoc %U http://geodesic.mathdoc.fr/item/IVM_1987_10_a4/ %G ru %F IVM_1987_10_a4